Optical system for real-time closed-loop control of fundus camera and implementation method therefor

ABSTRACT

An optical system for real-time closed-loop control of a fundus camera and an implementation method therefor. The optical system comprises an optical path structure composed of a fundus camera, light sources (LS 1 , LS 2 ), a plurality of lenses (L 1 , L 2 , L 2 ′, L 3 ′) and a dividing mirror (DM 1 , DM 2 ), and further comprises an orthogonal steering mirror group, which comprises: a first steering mirror (SM 1 ) moving in a horizontal direction and a second steering mirror (SM 2 ) moving in a vertical direction. The optical system converts fundus motion information obtained from a fundus camera image to residual motion information compensated by means of the first steering mirror (SM 1 ) and the second steering mirror (SM 2 ), uses a relationship between control parameters, and by means of a translation control instruction or/and the fundus rotation control instruction, operates the first steering mirror (SM 1 ) and the second steering mirror (SM 2 ) in real time to compensate for translational motion or/and controls the fundus camera to compensate for fundus rotation. By using the optical system and the implementation method therefor, and by improving the optical system of the fundus camera, the optical system is enabled to have a real-time closed-loop control function so as to implement real-time optical tracking of a fundus/retina position and a target.

FIELD OF THE INVENTION

The present invention relates to fundus target tracking and imagingtechnology in the medical field, and in particular, to an optical systemfor real-time closed-loop control of a fundus camera and animplementation method therefor.

BACKGROUND

A fundus camera is an eyeball base inspection tool commonly used toobserve the retina, optic disc, fundus capillary distribution, and thelike. The fundus camera may be used medically to screen the optic nerve,retina, choroid, and refractive media of the fundus for disease. At thesame time, the fundus camera may also assist in the diagnosis andcondition judgment of other diseases, such as screen a retinal image todetect cerebral infarction, cerebral hemorrhage, cerebralarteriosclerosis, cerebral tumor, diabetes, nephropathy, hypertension,retinopathy of prematurity, glaucoma, macular degeneration, and thelike. The sooner these diseases are detected, the more beneficial it isfor clinical treatment. Therefore, the fundus camera is an indispensablemedical device for clinical screening of fundus diseases.

However, the existing fundus camera usually does not have a real-timeclosed-loop control function, and thus cannot well support real-timeoptical tracking of the fundus position. Therefore, when using thefundus camera to obtain fundus position information to control anotherdevice to operate on the same fundus position, for example, to controloptical coherence tomography (OCT) to scan the same fundus position orto control the laser strike position of laser surgery, due to a motionof an eyeball and fundus (retina), it is difficult to accurately andreal-time control a spatial position of a light of the device on thefundus.

SUMMARY OF THE INVENTION

In view of this, the main objective of the present invention is toprovide an optical system for real-time closed-loop control of a funduscamera and an implementation method therefor, which intend to improvethe optical system for the fundus camera so that it has a real-timeclosed-loop control function to achieve real-time optically tracking offundus/retina position and target.

To achieve the above objective, the technical solution of the presentinvention is as follows:

An optical system for real-time closed-loop control of a fundus cameracomprises an optical path structure composed of a fundus camera, a lightsource, a plurality of lenses, and a dividing mirror, and furthercomprises an orthogonal steering mirror group, the orthogonal steeringmirror group comprising a first steering mirror SM1 moving in ahorizontal direction and a second steering mirror SM2 moving in avertical direction; the optical system converting fundus motioninformation obtained from an image of the fundus camera into residualmotion information that has been compensated by the SM1 and SM2, andmanipulating the SM1 and SM2 respectively in real time to compensate fora translational motion or/and control the fundus camera to compensatefor a fundus rotation by a translation control instruction and a fundusrotation control instruction using a relationship between controlparameters.

The relationship between the control parameters is expressed by equation(1):

(x _(t+1) ,y _(t+1),θ_(t+1))=(x _(t) ,y _(t),θ_(t))+g(Δx _(t) ,Δy_(t),Δθ_(t))  (1)

wherein (x_(t), y_(t)) is the translation control instructionaccumulated on the first steering mirror SM1 and the second steeringmirror SM2 at a current time point, θ_(t) is the fundus/retinal rotationcontrol instruction accumulated at the current time point; (Δx_(t),Δy_(t)) is a residual fundus translation amount obtained from the imageof the fundus camera, Δθ_(t) is a residual fundus rotation amountobtained from the image; (x_(t+1), y_(t+1)) is the translation controlinstruction that needs to be updated for the SM1 and SM2 at a nextsampling time point, θ_(t+1) is the fundus/retinal rotation controlinstruction that needs to be updated at the next sampling time point;index t represents a time sequence; g is a gain of the closed-loopcontrol system.

The control instructions for controlling the SM1 and SM2 are configuredto be sent from a personal computer or a dedicated processor connectedto the fundus camera of the optical system.

The SM1 and SM2 are a 6210H biaxial scanning mirror of CTI or anS334-2SL two-dimensional steering mirror of PI.

An implementation method based on the optical system for real-timeclosed-loop control of the fundus camera comprises the following steps:

A. disposing the orthogonal steering mirror group into the optical pathsystem, the orthogonal steering mirror group comprising the firststeering mirror SM1 moving in the horizontal direction and the secondsteering mirror SM2 moving in the vertical direction;

B. converting the fundus motion information obtained from the image ofthe fundus camera into the residual motion information that has beencompensated by the SM1 and SM2 using the optical system;

C. manipulating the SM1 and SM2 respectively in real time to compensatefor the translational motion or/and control the fundus camera tocompensate for the fundus rotation by the translation controlinstruction and the fundus rotation control instruction using therelationship between the control parameters.

An optical system for real-time closed-loop control of a fundus cameracomprises an optical path structure composed of a fundus camera, a lightsource, a plurality of lenses, and a dividing mirror, the fundus camerais disposed on an eyeball rotation signal compensation device; anorthogonal steering mirror group is disposed into the optical pathsystem, the orthogonal steering mirror group comprising a first steeringmirror SM1 moving in a horizontal direction and a second steering mirrorSM2 moving in a vertical direction; the optical system converting fundusmotion information obtained from an image of the fundus camera intoresidual motion information that has been compensated by the SM1 andSM2, and manipulating the SM1 and SM2 respectively in real time tocompensate for a translational motion or/and control the eyeballrotation signal compensation device to compensate for a fundus rotationby a translation control instruction and a fundus rotation controlinstruction using a relationship between control parameters.

The relationship between the control parameters is expressed by equation(1)′:

(x _(t+1) ,y _(t+1),θ_(t+1))=(x _(t) ,y _(t),θ_(t))+g(Δx _(t) ,Δy_(t),Δθ_(t))  (1)′

wherein (x_(t), y_(t)) is the translation control instructionaccumulated on the first steering mirror SM1 and the second steeringmirror SM2 at a current time point, θ_(t) is the rotation controlinstruction accumulated on the eyeball rotation signal compensationdevice at the current time point; (Δx_(t), Δy_(t)) is a residual fundustranslation amount obtained from the image of the fundus camera, Δθ_(t)is a residual fundus rotation amount obtained from the image of thefundus camera; (x_(t+1), y_(t+1)) is the translation control instructionthat needs to be updated for the SM1 and SM2 at a next sampling timepoint, θ_(t+1) is the fundus/retinal rotation control instruction thatneeds to be updated for the eyeball rotation signal compensation deviceat the next sampling time point; index t represents a time sequence; gis a gain of the closed-loop control system.

The eyeball rotation signal compensation device is a rotating stagecapable of rotating the fundus camera along an optical axis to opticallycompensate for the fundus rotation amount in real time.

The control instructions for controlling the SM1 and SM2 are configuredto be sent from a personal computer or a dedicated processor connectedto the fundus camera of the optical system.

The SM1 and SM2 are a 6210H biaxial scanning mirror of CTI or anS334-2SL two-dimensional steering mirror of PI.

An optical system for real-time closed-loop control of a fundus cameracomprises an optical path structure composed of a fundus camera, a lightsource, a plurality of lenses, and a dividing mirror, and the funduscamera is disposed on an eyeball rotation signal compensation device; anorthogonal steering mirror group is disposed into the optical pathsystem, the orthogonal steering mirror group comprising a first steeringmirror SM1 moving in a horizontal direction and a second steering mirrorSM2 moving in a vertical direction; the optical system obtaining areference image from the fundus camera, importing fundus positioninformation from outside or extracting it from a real-time video using across-correlation algorithm, obtaining an offset amount comprising atranslation amount and a rotation amount of any current image and thereference image by calculation; and manipulating the SM1 and SM2respectively in real time to compensate for a translational motionor/and control the eyeball rotation signal compensation device tocompensate for a fundus rotation by a translation control instructionand a fundus rotation control instruction using a relationship betweencontrol parameters.

The relationship between the control parameters is expressed by equation(1)″:

(x _(t+1) ,y _(t+1),θ_(t+1))=(x _(t) ,y _(t),θ_(t))+g(Δx _(t) ,Δy_(t),Δθ_(t))  (1)″

wherein (x_(t), y_(t)) is the translation control instructionaccumulated on the first steering mirror SM1 and the second steeringmirror SM2 at a current time point, θ_(t) is the rotation controlinstruction accumulated on the eyeball rotation signal compensationdevice at the current time point; (Δx_(t), Δy_(t)) is a residual fundustranslation amount obtained from the image of the fundus camera, Δθ_(t)is a residual fundus rotation amount obtained from the image of thefundus camera; (x_(t)+1, y_(t+1)) is the translation control instructionthat needs to be updated for the SM1 and SM2 at a next sampling timepoint, θ_(t+1) is the fundus/retinal rotation control instruction thatneeds to be updated for the eyeball rotation signal compensation deviceat the next sampling time point; index t represents a time sequence; gis a gain of the closed-loop control system.

The eyeball rotation signal compensation device is a mechanical devicecapable of compensating for an eyeball rotation signal in real time.

The control instructions for controlling the SM1 and SM2 are configuredto be sent from a personal computer or a dedicated processor connectedto the fundus camera of the optical system.

The SM1 and SM2 are a 6210H biaxial scanning mirror of CTI or anS334-2SL two-dimensional steering mirror of PI.

The optical system of the real-time closed-loop control of the funduscamera and implementation method therefor according to the presentinvention have the following beneficial effects.

1) The real-time closed-loop control of the optical system of the funduscamera according to the present invention obtains the fundus positioninformation from the fundus image signal collected by the fundus camera,including the translation amount of the eyeball/retina obtained from thefundus image and the rotation amount of the eyeball/retina obtained fromthe fundus image, converts the fundus position motion information intothe residual motion information which has been compensated by thesteering mirrors SM1 and SM2 in a closed-loop manner, so that it ispossible to determine the translation control instruction and rotationinstruction that need to be updated for the steering mirrors SM1 and SM2at the next sampling time point in a time-space domain through thetranslation control and rotation control instructions accumulated on thesteering mirror at the current time point and the residual fundustranslation and rotation amounts obtained from the fundus camera image,thereby determine a fundus/retinal motion (compensation) signal withhigh precision, high stability, and strong anti-interference ability forachieving the objective of closed-loop optical tracking of thefundus/retinal target using the fundus camera.

2) The present invention performs the closed-loop optical fundustracking using the fundus camera, firstly obtains the fundus motion(compensation) signal with high precision, high stability, and stronganti-interference ability, then converts the fundus motion signal into afundus motion (compensation) signal of a secondary optical systemthrough an appropriate spatial transformation relationship, and controlsa precise position of a light of the secondary optical system on thefundus/retina using this fundus motion (compensation) signal, and thisspatially transformed fundus motion (compensation) signal also hasclosed-loop signal characteristics of high precision, high stability andstrong anti-interference ability. The secondary optical system may be anOCT imaging system, and the position where the OCT scans the fundus is aspatial subset of an imaging position of the fundus camera; thesecondary optical system may also be a fundus laser treatment system. Inan embodiment of the present invention, the position where the laserstrikes the fundus is a spatial subset of the imaging position of thefundus camera. The secondary optical system can also be other opticalsystems used in different clinical applications.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an optical system of an existing funduscamera;

FIG. 2 is an example of a fundus image captured by an existing funduscamera;

FIG. 3 is a schematic diagram of an optical system in which an existingprimary fundus camera (i.e., a primary system) integrates a secondarysystem (i.e., an auxiliary system);

FIG. 4 is a schematic diagram of an optical system in which an existingprimary fundus camera (i.e., a primary system) integrates a plurality ofauxiliary systems;

FIG. 5 is a schematic diagram of an optical system structure forreal-time closed-loop control of a fundus camera according to a firstembodiment of the present invention;

FIG. 6 is a schematic structural diagram of an optical system forreal-time closed-loop control of a fundus camera according to a secondembodiment of the present invention;

FIG. 7 is a schematic diagram of a rotating imaging camera forcompensating rotational motion of a fundus according to the presentinvention;

FIG. 8 is a schematic diagram of an optical system in which a primaryfundus camera imaging system is used to implement closed-loop control ofa secondary system according to the first embodiment of the presentinvention;

FIG. 9 is a schematic diagram of an optical system in which a primaryfundus camera imaging system is used to implement closed-loop control ofa secondary system according to the second embodiment of the presentinvention;

FIG. 10 is a schematic diagram of a correspondence relationship betweenimaging spaces of the primary and auxiliary systems according to thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the technical solution of the present invention will befurther described in detail in connection with the drawings andembodiments of the present invention.

FIG. 1 is a schematic diagram of an optical system of an existing funduscamera. An incident light emitted from a light source (LS) 1 iscollimated by a lens L1 and reaches a dividing mirror (DM) 1. A portionof the incident light is reflected by the DM1 and enters a lens L2 toreach a fundus (Eye), namely a retina. The light reflected from thefundus transmits through the lens L2, the dividing mirror DM1, and afocusing lens L3, and is finally received by a fundus camera.

In an embodiment of the present invention, the fundus camera may beoperated independently, or may be operated by a PC or under the controlof a dedicated processor. The fundus camera shown in FIG. 1 may be usedto obtain an image of the fundus, as shown in FIG. 2. The image may becolorful or black-and-white.

FIG. 3 is a schematic diagram of an optical system in which an existingprimary fundus camera (i.e., a primary system, or known as a firstsystem) integrates a secondary system (i.e., an auxiliary system).

In a clinical application, a secondary optical system is usuallyintegrated into the primary fundus camera. In an embodiment of thepresent invention, a fundus camera with a function of closed-loopcontrol and real-time optical tracking of fundus position is defined asthe primary system; meanwhile, another optical system integrated intothe primary system, with common path or non-common path, is defined asthe auxiliary system.

As shown in FIG. 3, a light emitted by a light source LS2 of theauxiliary system reaches a dividing mirror DM2 after passing throughoptical elements of the auxiliary system, such as a lens L2 and scanningmirrors. In general, the DM2 transmits all light passing through theprimary system, but reflects all light of the auxiliary system. Theoptical elements in the auxiliary system, such as scanning mirrors, maybe controlled by the primary system or operated independently.

FIG. 4 is a schematic diagram of an optical system in which an existingprimary fundus camera (i.e., a primary system) integrates a plurality ofauxiliary systems.

As shown in FIG. 4, an optical system integrates a plurality ofauxiliary systems on the basis of FIG. 3. Each auxiliary system may haveits own specific function, for example, one is used for OCT (OpticalCoherence Tomography), and another one is used to project a focused beamonto the fundus for treatment purpose. The optical elements in eachauxiliary system, such as scanning mirrors and optical component, may becontrolled by the primary system or operated independently.

FIG. 5 is a schematic diagram of an optical system structure forreal-time closed-loop control of a fundus camera according to a firstembodiment of the invention.

In an embodiment of the present invention, by improving theabove-mentioned optical system structure of the fundus camera, theimproved optical system of the fundus camera has a function of real-timeclosed-loop control and optical tracking of the fundus position/retinaltarget.

As shown in FIG. 5, the optical system for real-time closed-loop controlof the fundus camera disposes an orthogonal steering mirror group, whichincludes two orthogonally moving one-dimensional steering mirrors (SM),specifically, a first steering mirror SM1 moving in a horizontaldirection and a second steering mirror SM2 moving in a verticaldirection. Obviously, the steering mirrors SM1 and SM2 may move in anydirection and angle in a 360-degree space, as long as the motion axes ofthe steering mirrors SM1 and SM2 satisfy an orthogonal relationship.

In an embodiment of the present invention, a 6210H biaxial scanningmirror of CTI (Cambridge Technology Inc) is used as the steering mirrorelements.

In another embodiment of the present invention, the steering mirrors SM1and SM2 may also be replaced with a two-dimensional steering mirror withtwo orthogonal motion axes. An implementable element is a S334-2SLtwo-dimensional steering mirror of PI (Physik Instrumente).

As shown in FIG. 5, a control instruction/signal (controlled by a PC)for controlling the steering mirrors SM1 and SM2 may be obtained fromthe PC or a dedicated processor.

A simple implementation is to apply a cross correlation algorithm toobtain a fundus position signal (x, y, θ) from a fundus image signalcollected by the fundus camera. The specific method is to use an imagepreviously obtained in time sequence from the fundus camera as areference image, and cross-correlate any image obtained subsequentlywith the reference image to obtain a relative displacement (x,y, θ),wherein (x, y) is a translation amount of the eyeball/retina obtainedfrom the fundus image, and θ is a rotation amount of the eyeball/retinaobtained from the fundus image. A method employed in an embodiment ofthe present invention is to calculate (x, y, θ) by using a crosscorrelation algorithm. A fundus image previously obtained in timesequence is used as a reference image, for example, defined as R, and afundus image subsequently obtained from the fundus camera at any timepoint is defined as T_(k), wherein the index k (=1, 2, 3, . . . ) is thetime sequence, which all occur after the reference image. Thecross-correlation algorithm xcorr(T_(k), R) is performed to obtain aspatial relative relationship (x, y, θ) between T_(k) and R. Performingthe cross-correlation algorithm xcorr (T_(k), R) may be implemented byconventional Fast Fourier Transform (FFT) or by other methods.

The above three parameters (x, y, θ) may generally describe a motion ofthe eyeball/fundus target relatively completely.

In the embodiment shown in FIG. 5, a closed-loop control method isdisclosed. The so-called closed-loop control means that the steeringmirrors SM1 and SM2 are disposed before the fundus camera as a signaldetector. Before the fundus image signal enters the fundus camera, animage drift caused by the fundus motion has been compensated by thesteering mirrors SM1 and SM2 in real time. Therefore, the image driftand rotation amount obtained by the fundus camera at any time point isactually residual motion information. As mentioned above, the residualmotion information is still obtained from the image through thecross-correlation algorithm. In this way, in a time-space domain, theabove-mentioned relationship of control parameters may be expressed in aform of equation (1):

(x _(t+1) ,y _(t+1),θ_(t+1))=(x _(t) ,y _(t),θ_(t))+g(Δx _(t) ,Δy_(t),Δθ_(t))  (1)

wherein (x_(t), y_(t)) is a translation control instruction accumulatedon the steering mirrors SM1 and SM2 at a current time point, θ_(t) is afundus/retinal rotation control instruction accumulated at the currenttime point (in a certain case, such as there is only translation withoutrotation, and thus θt is 0); (Δx_(t), Δy_(t)) is a residual fundustranslation amount obtained from the image of the fundus camera, Δθ_(t)is a residual fundus rotation (angle) amount obtained from the image;(x_(t+1), y_(t+1)) is the translation control instruction that needs tobe updated for the steering mirrors SM1 and SM2 at a next sampling timepoint, and θ_(t+1) is the fundus/retinal rotation control instructionthat needs to be updated (by controlling the fundus camera) at the nextsampling time point. Index t represents a time sequence, and g is a gainof the closed-loop control system.

In the above equation (1), the eyeball/retinal rotation signal may becompensated in a digital manner, or compensated in an optical-mechanicalmanner as shown in FIG. 6 below.

FIG. 6 is a schematic structural diagram of an optical system forreal-time closed-loop control of a fundus camera according to a secondembodiment of the present invention.

In the optical-mechanical compensation, one method is to mount thefundus camera on an eyeball rotation signal compensation device, such asa rotation stage, so that the fundus camera may rotate along an opticalaxis for real-time optical compensation of the fundus rotation amount.In this case, θ_(t) is the rotation control instruction accumulated onthe rotating stage at the current time point, Δθ_(t) is the residualfundus rotation amount obtained from the fundus camera image, andθ_(t+1) is the rotation control instruction that needs to be updated forthe rotating stage at the next sampling time point. In this embodiment,the remaining of the optical path structure is the same as that shown inFIG. 5.

As shown in FIG. 6, the optical system for real-time closed-loop controlof the fundus camera also provides another eyeball rotation signalcompensation device, such as a mechanical device for real-timecompensation of the eyeball rotation signal. In this embodiment, atwo-dimensional camera for imaging is mounted on a rotation stage (seethe dashed rectangular box), and the rotating axis of the rotation stageis consistent with the optical axis of the optical system.

As shown in equation (1), the method of obtaining the fundus positioninformation from the camera image usually employs a cross-correlationmethod. The method is to firstly select a reference image, import thefundus position information from an external file or extract it from areal-time video; in the following time sequence, calculate an offsetamount including a translation amount and a rotation amount of anyfuture current image and this reference image, such as (Δx_(t), Δy_(t),Δθ_(t)) in equation (1).

FIG. 7 is a schematic diagram of a rotating imaging camera forcompensating rotational motion of a fundus according to the presentinvention. The fundus rotation may be caused by many factors, includingeyeball rotation, head rotation or other reasons, but for a fundusimaging system, the final result is a rotation of the fundus image.Therefore, here are collectively referred to as fundus rotation.

As shown in FIG. 7, the lower part of FIG. 7A is the reference image,and the upper part is the position of the imaging camera. The lower partof FIG. 7B shows due to the rotation of the fundus, the image obtainedby the fundus camera also rotates, such as “rotate by 0 degree” in thefigure.

The cross-correlation algorithm obtains the rotation angle θ from theabove images in FIGS. 7A and 7B in a closed-loop manner from equation(1). Then, the angle θ may be sent to the rotation stage that controlsthe fundus (imaging) camera, to make a photosensitive surface of theimaging camera also rotate by θ degree to compensate for the rotationamount θ of the fundus. An equivalent result of the rotationcompensation is to restore the image obtained by the camera to theposition of the lower image in FIG. 7A.

FIG. 8 is a schematic diagram of an optical system in which a primaryfundus camera imaging system is used to implement closed-loop control ofa secondary system according to the first embodiment of the presentinvention.

As shown in FIG. 8, a closed-loop control fundus tracking signal of theprimary system is used to drive one or more similar optical-mechanicaldevices of the auxiliary system, so that the auxiliary system may alsoachieve the purpose of tracking the fundus position.

As shown in FIG. 8, the closed-loop control of the primary fundus cameraimaging system still employs the relationship of equation (1). In orderto achieve the purpose that the auxiliary system may also track theeyeball motion, the eyeball motion signal (x, y, θ) obtained by theprimary imaging system needs to be converted to the scanning mirrors ortracking mirrors of the auxiliary system. The tracking mirrors of theprimary imaging system, namely steering mirrors SM1 and SM2, are usedfor the tracking within the primary imaging system, and the scanningmirrors or tracking mirrors of the auxiliary system is used for theoptical tracking within the auxiliary system.

The spatial transformation relationship f(x, y, θ; x′, y′, θ′) betweenthe tracking mirrors SM1 and SM2 of the primary imaging system and thescanning mirrors of the auxiliary system is implemented by systemcalibration. As such, at any sampling time point, the control signalssent to the tracking mirrors of the auxiliary system according toequation (1) have the following relationship:

(x′ _(t+1) ,y′ _(t+1),θ′_(t+1))=f(x,y,θ;x′,y′,θ′)(x _(t+1) ,y_(t+1),θ_(t+1))  (2)

The result of the above equation (2) is used to adjust the position ofthe scanning mirrors of the auxiliary system to implement the real-timetracking of the target by the auxiliary system. However, this group ofsignals does not include the unique functions of the scanning mirrors ofthe auxiliary system used by itself, such as OCT scanning of the fundus.

FIG. 9 is a schematic diagram of an optical system in which a primaryfundus camera imaging system is used to implement closed-loop control ofa secondary system according to the second embodiment of the presentinvention.

As shown in FIG. 9, it is another embodiment of the present invention inwhich the optical tracking closed-loop control of the primary imagingsystem is used to drive the tracking of one or more auxiliary imagingsystems.

As shown in FIG. 9, the tracking mirrors of the primary imaging system,namely steering mirrors SM1 and SM2, are shared by all auxiliarysystems. In other words, after the real-time compensation of the SM1 andSM2, the eyeball motion signal reaching the auxiliary system has alsobeen compensated. If the auxiliary system is an imaging system, such asan OCT, the real-time image of the OCT has been stabilized by the SM1and SM2.

In FIG. 9, the scanning mirrors of the auxiliary system are only usedfor its own purposes, such as B-scan and C-scan of the OCT, or fornavigating the spatial position of the focused laser beam projected tothe fundus. However, there may also be some special reasons involved inthe design of the optical system. The primary system and the auxiliarysystem have different optical magnifications, spatial offsets amount andother reasons. As such, in order for the auxiliary system to accuratelytrack the fundus position, it is still necessary to use a spatialtransformation relationship such as equation (2) to convert the eyeballmotion information of the primary system to the scanning mirrors of theauxiliary system to implement the optical tracking of the auxiliarysystem.

FIG. 10 is a schematic diagram of a correspondence relationship betweenimaging spaces of the primary and auxiliary systems according to thepresent invention.

As shown in FIG. 10, it is assumed that the size of the imaging surfaceof the primary optical system is exactly twice the size of the imagingsurface of the auxiliary system, and the imaging center positions of thetwo systems are consistent with each other. This is very common inclinical practice, for example, the auxiliary system “digging out” alocal area from the primary system for optical/digital magnification, orother forms of imaging. Then, when using the spatial transformationrelation of equation (2), it is easy to obtain:

x′ _(t+1) =x _(t+1)/2  (3)

y′ _(t+1) =y _(t+1)/2  (4)

θ′_(t+1)=θ_(t+1)  (5)

Obviously, the spatial mapping relationship between the primary systemand the auxiliary system in the above equations (3), (4), and (5) mayalso have other forms than FIG. 10, then equations (3)-(5) obtained fromequation (2) have different results.

Once the design of the optical system is determined, this certainrelationship may generally be obtained by one-time calibrationmeasurement and calculation.

The foregoing descriptions are only preferred embodiments of the presentinvention, and are not used to limit the protection scope of the presentinvention.

1. An optical system for real-time closed-loop control of a funduscamera, comprising an optical path structure composed of a funduscamera, a light source, a plurality of lenses, and a dividing mirror,and characterized by further comprising an orthogonal steering mirrorgroup, the orthogonal steering mirror group comprising a first steeringmirror SM1 moving in a horizontal direction and a second steering mirrorSM2 moving in a vertical direction; the optical system is arranged toconvert fundus motion information obtained from an image of the funduscamera into residual motion information that has been compensated by theSM1 and SM2, and to manipulate the SM1 and SM2 respectively in real timeto compensate for a translational motion or/and control the funduscamera to compensate for a fundus rotation by a translation controlinstruction and a fundus rotation control instruction using arelationship between control parameters.
 2. The optical system forreal-time closed-loop control of the fundus camera according to claim 1,characterized in that the relationship between the control parameters isexpressed by equation (1):(x _(t+1) ,y _(t+1),θ_(t+1))=(x _(t) ,y _(t),θ_(t))+g(Δx _(t) ,Δy_(t),Δθ_(t))  (1) wherein (x_(t), y_(t)) is the translation controlinstruction accumulated on the first steering mirror SM1 and the secondsteering mirror SM2 at a current time point, θ_(t) is the fundus/retinalrotation control instruction accumulated at the current time point;(Δx_(t), Δy_(t)) is a residual fundus translation amount obtained fromthe image of the fundus camera, Δθ_(t) is a residual fundus rotationamount obtained from the image; (x_(t+1), y_(t+1)) is the translationcontrol instruction that needs to be updated for the SM1 and SM2 at anext sampling time point, θ_(t+1) is the fundus/retinal rotation controlinstruction that needs to be updated at the next sampling time point;index t represents a time sequence; g is a gain of the closed-loopcontrol system.
 3. The optical system for real-time closed-loop controlof the fundus camera according to claim 1, characterized in that thecontrol instructions for controlling the SM1 and SM2 are configured tobe sent from a personal computer or a dedicated processor connected tothe fundus camera of the optical system.
 4. The optical system forreal-time closed-loop control of the fundus camera according to claim 1,characterized in that the SM1 and SM2 are a 6210H biaxial scanningmirror of CTI or an S334-2SL two-dimensional steering mirror of PI. 5.(canceled)
 6. An optical system for real-time closed-loop control of afundus camera, comprising an optical path structure composed of a funduscamera, a light source, a plurality of lenses, and a dividing mirror,and characterized by the fundus camera is disposed on an eyeballrotation signal compensation device; an orthogonal steering mirror groupis disposed into the optical path system, the orthogonal steering mirrorgroup comprising a first steering mirror SM1 moving in a horizontaldirection and a second steering mirror SM2 moving in a verticaldirection; the optical system is arranged to convert fundus motioninformation obtained from an image of the fundus camera into residualmotion information that has been compensated by the SM1 and SM2, and tomanipulate the SM1 and SM2 respectively in real time to compensate for atranslational motion or/and control the eyeball rotation signalcompensation device to compensate for a fundus rotation by a translationcontrol instruction and a fundus rotation control instruction using arelationship between control parameters.
 7. The optical system forreal-time closed-loop control of the fundus camera according to claim 6,characterized in that the relationship between the control parameters isexpressed by equation (1)′:(x _(t+1) ,y _(t+1),θ_(t+1))=(x _(t) ,y _(t),θ_(t))+g(Δx _(t) ,Δy_(t),Δθ_(t))  (1)′ wherein (x_(t), y_(t)) is the translation controlinstruction accumulated on the first steering mirror SM1 and the secondsteering mirror SM2 at a current time point, θ_(t) is the rotationcontrol instruction accumulated on the eyeball rotation signalcompensation device at the current time point; (Δx_(t), Δy_(t)) is aresidual fundus translation amount obtained from the image of the funduscamera, Δθ_(t) is a residual fundus rotation amount obtained from theimage of the fundus camera; (x_(t+1), y_(t+1)) is the translationcontrol instruction that needs to be updated for the SM1 and SM2 at anext sampling time point, θ_(t+1) is the fundus/retinal rotation controlinstruction that needs to be updated for the eyeball rotation signalcompensation device at the next sampling time point; index t representsa time sequence; g is a gain of the closed-loop control system.
 8. Theoptical system for real-time closed-loop control of the fundus cameraaccording to claim 6, characterized in that the eyeball rotation signalcompensation device is a rotating stage capable of rotating the funduscamera along an optical axis to optically compensate for the fundusrotation amount in real time.
 9. The optical system for real-timeclosed-loop control of the fundus camera according to claim 6,characterized in that the control instructions for controlling the SM1and SM2 are configured to be sent from a personal computer or adedicated processor connected to the fundus camera of the opticalsystem.
 10. The optical system for real-time closed-loop control of thefundus camera according to claim 6, characterized in that the SM1 andSM2 are a 6210H biaxial scanning mirror of CTI or an S334-2SLtwo-dimensional steering mirror of PI.
 11. An optical system forreal-time closed-loop control of a fundus camera, comprising an opticalpath structure composed of a fundus camera, a light source, a pluralityof lenses, and a dividing mirror, and characterized by the fundus camerais disposed on an eyeball rotation signal compensation device; anorthogonal steering mirror group is disposed into the optical pathsystem, the orthogonal steering mirror group comprising a first steeringmirror SM1 moving in a horizontal direction and a second steering mirrorSM2 moving in a vertical direction; the optical system is arranged toobtain a reference image from the fundus camera, to import fundusposition information from outside or extract it from a real-time videousing a cross-correlation algorithm, to obtain an offset amountcomprising a translation amount and a rotation amount of any currentimage and the reference image by calculation; and to manipulate the SM1and SM2 respectively in real time to compensate for a translationalmotion or/and control the eyeball rotation signal compensation device tocompensate for a fundus rotation by a translation control instructionand a fundus rotation control instruction using a relationship betweencontrol parameters.
 12. The optical system for real-time closed-loopcontrol of the fundus camera according to claim 11, characterized inthat the relationship between the control parameters is expressed byequation (1)″:(x _(t+1) ,y _(t+1),θ_(t+1))=(x _(t) ,y _(t),θ_(t))+g(Δx _(t) ,Δy_(t),Δθ_(t))  (1)″ wherein (x_(t), y_(t)) is the translation controlinstruction accumulated on the first steering mirror SM1 and the secondsteering mirror SM2 at a current time point, θ_(t) is the rotationcontrol instruction accumulated on the eyeball rotation signalcompensation device at the current time point; (Δx_(t), Δy_(t)) is aresidual fundus translation amount obtained from the image of the funduscamera, Δθ_(t) is a residual fundus rotation amount obtained from theimage of the fundus camera; (x_(t+1), y_(t+1)) is the translationcontrol instruction that needs to be updated for the SM1 and SM2 at anext sampling time point, θ_(t+1) is the fundus/retinal rotation controlinstruction that needs to be updated for the eyeball rotation signalcompensation device at the next sampling time point; index t representsa time sequence; g is a gain of the closed-loop control system.
 13. Theoptical system for real-time closed-loop control of the fundus cameraaccording to claim 11, characterized in that the eyeball rotation signalcompensation device is a mechanical device capable of compensating foran eyeball rotation signal in real time.
 14. The optical system forreal-time closed-loop control of the fundus camera according to claim11, characterized in that the control instructions for controlling theSM1 and SM2 are configured to be sent from a personal computer or adedicated processor connected to the fundus camera of the opticalsystem.
 15. The optical system for real-time closed-loop control of thefundus camera according to claim 11, characterized in that the SM1 andSM2 are a 6210H biaxial scanning mirror of CTI or an S334-2SLtwo-dimensional steering mirror of PI.